Lights for illuminating large areas such as roads, parking lots, fields, and the like have long been provided. Lighting technology for such lights has progressed from incandescent to specialized high powered types such as sodium vapor and mercury vapor. However, it has become desirable to utilize more efficient light sources, as efficiency relates to units of light output per unit of electrical input.
Light emitting diodes (hereinafter LEDs) are among the most efficient types of light sources commercially available today. LEDs enjoy not only relatively high efficiency, but offer long life and relatively uncomplicated construction. LEDs have progressed to the point where white light producing LEDs could be employed in many applications, including overhead or elevated lighting such as that suitable for roads, parking lots, fields, and the like.
LEDs require suitable heat sinks to dissipate heat generated by the LEDs. Heat sinks are advantageously fabricated by extruding them from aluminum or an aluminum alloy. It would be desirable to provide lenses for LEDs which are formed to accommodate extruded heat sinks.
It would also be desirable to provide lenses which project light in rectangular beams, when the beam is viewed in cross section. This promotes more even lighting than is provided by circular beams. When plural circular beams impinge upon an environmental surface, there are gaps in coverage where between the circular light patches. Alternatively, where circular beams overlap, there are areas where only one beam contributes its light, so that lighting is still uneven. There exists a need for a lens which projects rectangular beams, particularly for lens holders such as heat sinks, and also for serial arrangements of light sources and lenses.